Automatic sprinkler systems for fire protection of structures such as office buildings, warehouses, hotels, schools and the like are required when there is a significant amount of combustible matter present in the structure. The combustible matter may be found in the materials from which the building itself is constructed, as well as in the building contents, such as furnishings or stored goods.
FIG. 1 shows a schematic diagram of a fire suppression sprinkler system 10 comprising sprinkler heads 12 attached to a piping network 14 that extends through the structure (not shown) to be protected. Piping network 14 is connected to a source of pressurized water 16 or other fire suppressing fluid through a control valve 18. An actuator 20 controls the opening of valve 18 in response to changes in one or more physical parameters indicative of a fire, such as a pressure change within the piping network, or a temperature rise within the structure as described below. Various types of actuators may be used, such as those disclosed in U.S. Pat. Nos. 6,378,616, 6,666,277 and 6,708,771, all of which are hereby incorporated by reference.
The fire suppression system 10 described herein may be of any type, but the dry system is preferred as it finds widespread and effective use. Dry systems use the actuator 20, which responds to one or more signals from different detectors to open the valve 18 and provide water to the piping network 14. Similar to the so-called “deluge” or “pre-action” systems, prior to actuation, the piping network 14 is normally filled with pressurized air or nitrogen from a source of pressurized gas 22, such as a compressor or gas tanks. The dry system can thus be used in unheated environments which are subject to below freezing temperature without fear of pipes bursting due to water within the pipes expanding upon freezing.
When sufficiently pressurized, the behavior of the gas within the piping network may be used to indicate a fire condition and trigger actuation of the dry system. Heat from the fire will cause sprinkler heads to open, allowing pressurized gas to escape from the piping network and result in a pressure drop within the system. The actuator 20 is connected to the piping network by a conduit 24, which allows the actuator to sense the pressure drop and trigger the system by opening valve 18 in response. The actuator may also require an additional, independent signal indicative of a fire, such as a signal from a temperature sensor 26, before it opens valve 18. Such systems are known as double interlock preaction systems, and are advantageous because they prevent unintentional discharge of water due to failure, breakage or accidental opening of a sprinkler head.
FIG. 2 shows a control valve 28 according to the prior art, used with fire suppression sprinkler systems. Valve 28 has an inlet 30 connected to the pressurized water source 16 and an outlet 32 connected to the piping network 14. A clapper 34 is pivotally mounted within the valve. Pivoting motion of the clapper opens and closes the inlet controlling the flow of fluid to the system. When the inlet is pressurized, the clapper will open in response to the pressure and, therefore, must be held closed by a latch 36 pivotally mounted within the valve. Latch 36 is held in engagement with the clapper 34 by a piston 38 reciprocably movable within a cylinder 40. Piston 38 is preferably biased by a spring 42 to move away from and release latch 36, but the piston is held engaged with the latch by water pressure provided by a conduit 44 connecting the inlet to the cylinder. A conduit 46 connects the cylinder 40 to the actuator 20. When the actuator receives signals indicative of a fire, it releases the pressure within cylinder 40, allowing the piston 38 to move under the biasing force of spring 42 and release latch 36. This allows clapper 34 to open and provide water to the piping network 14. Note that spring 42 may be omitted if the geometries of the clapper 34 and the latch 36 relative to one another and their axes of rotation are such that water pressure in inlet 30, acting on the clapper, will pivot the latch and drive the piston 38 into the cylinder 40 in the absence of sufficient counteracting pressure within the cylinder.
Control valves 28 according to the prior art suffer a disadvantage in that they are complicated and expensive to manufacture and maintain. There is clearly a need for a simpler valve design with fewer moving parts that may be used in fire suppression systems.